Process for the production of acrylonitrile polymer fibers



Sept. 4, 1956 w. D. JONES ET AL 2,761,754

PROCESS FOR THE PRODUCTION OF ACRYLONITRILE POLYMER FIBERS Filed June 7, 1952 OIL 1* FIGJ. 3 I AIR I PIPE SAND PACK 1 l7 BLOWER ANDSCREENS 2 JET i /5 OIL SUPERHEATED STEAM CABINET LU BRICATING ROLLER FIG.2.

' INVENTORS. RING SPINNER WILFORD DONALD JONES BOBB'N CHARLES E. KAUFMAN,JR.

PROCESS FOR THE PRODUCTION OF ACRYLO- NITRILE POLYMER FIBERS Wilford Donald Jones, Summit, and Charles E. Kaufman, In, Montclair, N. J., assignors to Celanese Corporation of America, New York, N. Y., a corporation of Delaware Application June 7, 1952, Serial No. 292,274

'10 Claims. (Cl. 18-54) This invention relates to the production of acrylo' nitrile polymer yarns and more particularly to a process for the production of acrylonitrile polymer yarns from solutions of acrylonitrile polymers containing at least 85 acrylonitrile in the polymer molecule.

Filaments and yarns produced from polyacrylonitrile and copolymers of acrylonitrile with other monomers in which at least 85% of the polymer is acrylonitrile are known to the art. Such filaments are generally produced by dry spinning wherein a solution of the acrylonitrile polymer in a high-boiling organic solvent is extruded through a spinneret into an evaporative medium to remove substantially all the solvent, or by wet spinning wherein a solution of the acrylonitrile polymer in a solvent is extruded through a spinneret into a coagulating liquid which is miscible with the solvent. These prior processes required the use of exceptionally high temperatures or unduly large or elaborate apparatus.

It is an object of our invention to provide an improved process for the production of filaments from acrylonitrile polymers.

It is a further object of our invention to provide a process for the production of filaments from solutions of acrylonitrile polymers without the use of excessively high temperatures or unduly large or elaborate apparatus.

Another object of our invention is the provision of an improved process for starting the spinneret in the spinning of hot solutions of acrylonitrile polymers.

Still another object of our invention is the provision of an improved process for drawing or stretching filaments of acrylonitrile polymers in order to increase their tenacity.

Other objects of our invention will appear from the following detailed description.

In accordance with the process of our invention a solution of an acrylonitrile polymer containing at least 85% acrylonitrile is extruded through a jet or spinneret into a column of heated air or other evaporative medium. The solvent is preferably organic, high-boiling and water-miscible. The filaments emerging from the spinneret are drawn down through the column of evaporative medium 'such as air until the solvent content is about 20 to 40%, preferably 25 to 40%, based on the Weight of the filament. The surfaces of the filaments are then wet thoroughly with a non-solvent for the polyacrylonitrile, which non-solvent is miscible with the solvent in the filament. The non-solvent is preferably wa ter, which preferably contains an anti-static agent and a textile lubricant.

The solvent containing filaments are then washed to' remove all the solvent remaining therein, preferably with hot water. During this washing step the filaments are prevented by any suitable expedient from shrinking substantially in length. The resulting yarn may then be drawn or stretched to produce high tenacity filaments. After the yarn has been drawn it may be relaxed by passing it through a heated medium, such as hot air,

nited States Patent 2 while allowing some shrinkage. This improves the elongation of the yarn.

In carrying out our invention we employ a solution of any soluble homopolymer or copolymer of acrylonitrile containing at least acrylonitrile. Suitable copolymers are copolymers of acrylonitrile with vinyl acetate, vinyl propionate, vinyl butyrate, vinyl chloride, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, higher alkyl acrylates and methacrylates, amides such as acrylamide, methacrylamide and N-ethyl acrylamide, methacrylonitrile, dimethyl maleate, diethyl fumarate, styrene, isobutylene, or butadiene, as Well as with other ethyleuically unsaturated monomers. We prefer to employ high boiling water-miscible solvents. Examples of solvents which may be used are amides, lactone, sulfones, sulfolanes, nitriles or cyclic carbonates, such as dimethyl formamide, N,N-dimethyl acetamide, gamma butyrolactone, N-formyl pyrrolidine, dimethyl sulfone, ethyl methyl sulfone, sulfolane, fumaronitrile or ethylene carbonate. The solvent desirably has a boiling point above 140 C. Dimethyl formamide is the preferred solvent. The concentration of the polymer in the solution is not critical. Preferably, it ranges from 10 to 30%; a concentration of about 19- 22% gives optimum results.

The solution of the acrylonitrile polymer is maintained at an elevated temperature, such as in the range of about 80 to C., and forced through a hot spinneret or spinning jet into an evaporative atmosphere, such as hot air. We have found it very desirable to force the heated solution through a bed of finely-divided inert granular material, such as a sand pack, just before it passes through the jet or spinneret. This expedient acts to disperse and homogenize any solvent-polymer gel particles, which might otherwise cause uneven or broken filaments. Of course, the sand pack also removes dirt and other solid matter.

It is desirable that the jet contain several openings so that a plurality of filaments are extruded at the same time.

The face of the jet or spinneret is preferably coated with graphite, which may be applied as a thin layer of a mixture of graphite and a wax, such as the mixture, containing 40% of graphite and the balance of a low melting point wax, known as Dixons Graphite Slip Stik, in which the wax has a melting point of about 48 C. In the spinning of hot solutions of acrylonitrile polymers great difficulty has been encountered in starting, since the individual filaments being extruded from the hot face of the jet'or spinneret tend to coalesce to form a tenacious mass which adheres to the hot face. Conventional methods of starting jets, such as by wiping with lubricating oils or various other liquids, have not proved suitable for the spinning of hot solutions of acrylonitrile polymers. Application of liquids and greases, such as silicone oils, silicone greases, dimethyl formamide and conventional yarn lubricants, all failed. It has been suggested that the jet be started under water, but this has proved impracticable with hot spinnerets. The application of graphite to the face of the jet completely eliminates all starting troubles and additionally makes it possible to spin hot solutions of acrylonitrile polymers for long periods of time without any and Fig. 2 shows a diagrammatic form of one embodiment of a stretching device suitable for use in our invention.

In Fig. 1 there is shown the sand pack and screens 1 and a spinning jet 2 supported within a spinning cell 3, which is surrounded by jacket 4. The hot acrylonitrile polymer solution is forced, by means of a booster pump and metering pump (not shown), through the sand packs and screens 1 and then, in the form of thin streams, through spinning jet 2 and into the spinning cell 3, where the filaments are formed. Spinning cell 3 is heated by hot oil circulated through jacket 4. Air is forced by blower through pipe 17 and heater 16, into the spinning cell 3. This air is admitted at two points, one above the jet 2 through air pipe 5 and one about halfway down spinning cell 3 through air pipe 6. The air is removed through pipe 6A with the aid of a suction blower (not shown). The filaments travel down through the spinning cell 3 and through low friction ring guide 7. Immediately thereafter, the filaments, which at this point contain to 40% of solvent, pass over a driven lubricating or furbishing roll 8 which rotates in a pan 9 containing the non-solvent for the polymer. Lubricating roller 8 is arranged so that the surfaces of the filaments are wet thoroughly by the non-solvent. The filaments, which are now in the form of a multifilament yarn, pass over a driven take-up roll 10 and around a driven take-up roll 11 and a separator pin 12, take-up roll 11 being driven at the same peripheral speed as take-up roll 10, and are then Wound, while still wet with water, on a perforated bobbin 13 mounted in a ring spinner 14, which is driven at a speed such that some twist is imparted to the yarn.

In Fig. 2 there is shown a wick 18, a draw roll 19 and a separator roll 20. The washed solvent-free yarn is passed over the wick 18 where anti-static conditioning agent is applied, around draw roll 19 and separator roll 20, then through a cabinet 23, which has an inlet and an outlet for superheated steam, and around a draw roll 22 and separator roll 21. Draw roll 22 is driven at a speed several times that of draw roll 19 in order to stretch the yarn. Heater 24 is provided for heating the draw roll 19 in order to preheat the filaments before they enter the cabinet 23.

In order further to illustrate our invention but without being limited thereto, the following examples are given:

Example I 1000 parts by weight of dimethyl formamide are cooled to about 25 C. 277 parts of polyacrylonitrile of intrinsic viscosity of 2.0, ground to 100 mesh size, are added slowly with stirring to the cold dimethyl formami-de. The resulting fluid slurry is placed on a hot water bath, stirred continuously, and the temperature gradually increased. After about 3 hours the mixture becomes a honey colored viscous solution, which is further heated to 130 C. on an oil bath with frequent stirring. The hot solution is forced through a candle filter under nitrogen pressure and then allowed to stand for about 8 hours to degasify it. It is then forced by a booster pump and metering pump through the heated pipes at a rate of 26.3 cc. per minute and through a sand pack which comprises an upper layer of 4060 mesh sand, an intermediate layer of 60-80 mesh sand and a bottom layer of 100-120 mesh sand supported on a 250 mesh screen, which is in turn supported by a 50 mesh screen just above an electrically heated spinning jet, which is at a temperature of about 123 C. The spinning jet is made of stainless steel, and has 10 holes each 0.005

of a spinning apparatus suitable for use in our invention,

inch in diameter. The outer face and holes of the jet are coated with a thin layer of Dixons Graphite Slip Stik. The polyacrylonitrile solution streams cleanly through all the holes of the spinning jet from the very start. There is no tendency for the solution to stick to the jet or for the streams to coalesce. The streams of solution or filaments are drawn down through the spinning cell which is heated by circulation of oil at 250 C. through its jackets. Heated air, at a temperature of about 124 C. is blown in at the top of the cell past the spinning jet and at about half way down the spinning cell. The air is blown through the cell at a rate of about cu. ft. per minute. The temperature of the air rises to about 220 C. near the bottom of the spinning cell. The filaments are led out through the bottom of the cell through a suitable low friction guide and over a driven lubricating roller which applies a 5% solution in water of a mixture of 15 parts of triethanolamine, 30 parts of a partial ester of n-decyl alcohol and phosphoric acid containing an average of about 1.5 n-decyl radicals per phosphorous atom, 5 parts of a polyethylene glycol monester of oleic acid containing 8-10 ethylene glycol residues, and 950 parts of water. Here the aqueous lubricant, which has a temperature of about 30 C., thoroughly wets all the surfaces of the filaments. The filaments are passed over a take-up roller and then around a second take-up roller and separator. The take-up rollers are each driven at the same peripheral speed of about 250 meters per minute. The yarn, which now has a dimethyl formamide content of 29-30%, is wound on a perforated bobbin and given a twist of 2.0 turns per inch by means of a ring spinner. After winding, the bobbin is removed from the ring spinner and water at a temperature of 85 C. is passed through the bobbin from the center outwardly for /2 hour. The resulting denier solvent-free yarn is passed over a wick immersed in a bath of an anti-static textile conditioning agent and to a first drawing roll maintained at a temperature of 130 C., then through a cabinet filled with superheated steam at atmospheric pressure and at a temperature of about 176 C. and over a cold drawing roll rotating at a peripheral speed several times that of the first drawing roll. When the drawing ratio is 6.0, that is, when the second drawing roll rotates at six times the peripheral speed of the first drawing roll and the yarn is stretched to 6 times its original length, the resulting yarn, of 28.6 denier, has an elongation at break of 8.2% and a tensile strength of 4.9 grams per denier.

Example 11 The procedure of Example I is repeated except that the step of filtering through a candle filter is eliminated, the concentration of polyacrylonitrile in the spinning solution is 19.2%, the metering pump operates at 26.6 cc. per minute, the take-up rolls have a peripheral speed of 240 meters per minute, the entering air is heated to 172 C. and reaches a maximum of about 219 C. and the temperature of the jet is about 137 C. The yarn wound on the perforated bobbin has a solvent content of 35%. After washing, the solvent-free yarn has an elongation of 20.9%, a tenacity of 0.72 gram per denier, and a denier of 171.3. The yarn is then stretched continuously in travelling from a cold first drawing roll through a chamber containing superheated steam at atmospheric pressure and at a temperature of 180 C. and then over a cold second drawing roll operating at a peripheral speed several times that of the first drawing roll, the specific speed ratio depending on the product desired. When stretched to six times its original length the drawn fiber has a tenacity of 5.3 grams per denier, and an elongation of about 8.8%. I

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the production of acrylonitrile polymer fibers, which comprises extruding in the form of a filament a solution of a soluble acrylonitrile polymer containing at least 85% acrylonitrile in a water-miscible solvent therefor into and through a zone containing an evaporative medium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying an aqueous medium to Wet thoroughly the surface of the solvent-containing filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the solvent-containing filament by washing the same with an aqueous medium while preventing any substantial lengthwise contraction of the filament.

2. Process for the production of acrylonitrile polymer fibers, which comprises extruding in the form of a filament a solution of a soluble acrylonitrile polymer containing at least 85% acrylonitrile in a water-miscible solvent therefor which has a boiling point of at least 140 C. into and through a zone containing an evaporative medium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying a cool aqueous medium to wet thoroughly the surface of the solvent-containing filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filament on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solvent-containing filament by washing the same with an aqueous medium while preventing any substantial lengthwise contraction of the filament.

3. Process for the production of acrylonitrile polymer fibers, which comprises extruding in the form of a filament a solution of a soluble acrylonitrile polymer containing at least 85% acrylonitrile in a Water-miscible solvent therefor which has a boiling point of at least 140 C. into and through a zone containing an evaporative medium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying a cool aqueous medium containing an antistatic agent to wet thoroughly the surface of the solvent containing filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solvent-containing filament by washing the same with an aqueous medium while preventing any substantial lengthwise contraction of the filament.

4. Process for the production of acrylonitrile polymer fibers, comprising the steps of extruding in the form of a filament a solution of a soluble acrylonitrile polymer containing at least 85% acrylonitrile in a water-miscible solvent therefor which has a boiling point of at least 140 C. into and through a zone containing an evaporative medium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying a cool aqueous medium containing an anti-static agent and a textile lubricant to wet thoroughly the surface of the solvent-containing filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solvent-containing filament by washing the same with an aqueous medium while preventing any substantial lengthwise contraction of the filament.

5. Process for the production of acrylonitrile polymer fibers which comprises extruding in the form of a filament a solution of a soluble acrylonitrile polymer containing at least acrylonitrile in a water-miscible slovent therefor which has a boiling point of at least C. into and through a zone containing an evaporative medium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying a cool aqueous medium containing an anti-static agent to wet thoroughly the surface of the solvent containing filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solvent-containing filament by washing with water while preventing any substantial lengthwise contraction of the filament.

6. Process for the production of acrylonitrile polymer fibers, which comprises extruding in the form of a filament a solution of a soluble acrylonitrile polymer containing at least 85% acrylonitrile in a water-miscible solvent therefor which has a boiling point of at least 140 C. into and through a zone containing an evaporative medium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying a cool aqueous medium containing an anti-static agent and a textile lubricant to wet thoroughly the surface of the solvent-containing filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solvent-containing filament by washing with hot water while preventing any substantial lengthwise contraction of the filament.

7. Process for the production of acrylonitrile polymer fibers, which comprises extruding in the form of a filament a solution of a soluble acrylonitrile polymer containing at least 85 acrylonitrile in a water-miscible solvent therefor into and through a zone containing an evaporative medium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying an aqueous medium to wet thoroughly the surface of the solvent-containing filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, efiecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solvent-containing filament by washing the same with an aqueous medium while preventing any substantial lengthwise contraction of the filament and stretching the filament by about 300% to 1100% through an atmosphere of superheated steam which is at a temperature of at least 140 C. and not more than 30 C. below the tacky point of the acrylonitrile polymer.

8. Process for the production of polyacrylonitrile fibers, which comprises extruding in the form of a filament :1 solution of polyacrylonitrile in a water-miscible solvent therefor which has a boiling point of at least 140 C. into and through a zone containing heated air, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying cool aqueous medium containing an anti-static agent to wet thoroughly the surface of the solvent-containing filament leaving said zone so as to efiect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solvent-containing filament by washing with hot water while preventing any substantial lengthwise contraction of the filament.

9. Process for the production of polyacrylom'trile fibers, which comprises extruding in the form of a filament a solution of polyacrylonitrile in dimethyl formamide into and through a zone containing heated air, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying a cool aqueous medium containing an anti-static agent to wet thoroughly the surface of the filament leaving said zone so as to effect a hardening of the surface of said filament, winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and effecting the second stage of solvent removal by removing substantially all of the remainder of the dimethyl formamide from the filament by washing with hot water while preventing any substantial lengthwise contraction of the filament.

10. Process for the production of acrylonitrile polymer fibers, comprising the steps of forcing a solution of a soluble acrylonitrile polymer containing at least acrylonitrile in a water-miscible solvent therefor through a bed of finely divided inert granular material and immediately thereafter through a spinneret, the ten-"face of which is coated with graphite, into and through a zone a My n y s containing an evaporhtrveineclium, removing substantially all of the solvent in two stages, the first stage of removal of the solvent comprising evaporating the solvent in said zone under such conditions that the filament leaving said zone contains 20 to 40% of the solvent, based on the weight of the filament, applying an aqueous medium to wet thoroughly the surface of the solvent-containing filament leaving said zone so as to effect a hardening of the surface of said filament, Winding said filament to form a package, the hardening of the filament with the aqueous medium acting to prevent coalescence of the filaments on the package, and efiecting the second stage of solvent removal by removing substantially all of the remainder of the solvent from the wet solventcontaining filament by washing the same with an aqueous medium while preventing any substantial lengthwise contraction of the filament.

References Cited in the file of this patent UNITED STATES PATENTS 2,060,048 Dreyfus Nov. 10, 1936 2,068,538 Dreyfus et al. Jan. 19, 1937 2,266,368 Hull et al. Dec. 16, 1941 2,558,732 Cresswell July 3, 1951 2,564,308 Nagel Aug. 14, 1951 2,605,502 Culpeper et al. Aug. 5, 1952 2,607,751 Flanagan Aug. 16, 1952 2,615,198 Flannagan Oct. 28, 1952 2,622,003 Hoxie Dec. 16, 1952 

1. PROCESS FOR THE PRODUCTION OF ACRYLONITRILE POLYMER FIBERS, WHICH COMPRISES EXTRUDING IN THE FORM OF A FILAMENT A SOLUTION OF A SOLUBLE ACRYLONITRILE POLYMER CONTAINING AT LEAST 85% ACRYLONITRILE IN A WATER-MISCIBLE SOLVENT THEREFOR INTO AND THROUGH A ZONE CONTAINING AN EVAPORATIVE MEDIUM REMOVING SUBSTANTIALLY ALL OF THE SOLVENT IN TWO STAGES, THE FIRST STAGE OF REMOVAL OF THE SOLVENT COMPRISING EVAPORATING THE SOLVENT IN SAID ZONE UNDER SUCH CONDITIONS THAT THE FILAMENT LEAVING SAID ZONE CONTAINS 20 TO 40% OF THE SOLVENT, BASED ON THE WEIGHT OF THE FILAMENT, APPLYING AN AQUEOUS MEDIUM TO WET THOROUGHLY THE SURFACE OF THE SOLVENT-CONTAINING FILAMENT LEAVING SAID ZONE SO AS TO EFFECT A HARDENING OF THE SURFACE OF SAID FILAMENT, WINDING SAID FILAMENT TO FORM A PACKAGE, THE HARDENING OF THE FILAMENT WITH THE AQUEOUS MEDIUM ACTING TO PREVENT COALESCENCE OF THE FILAMENTS ON 